A 35 mm roll film, which is in wide use, is accommodated in a light-tight container, which is called a patrone. In this case, a long film is used, and holes, which are called perforations, are successively provided on both sides of the film. A base end of the film is fixed to a spool shaft provided in the patrone and the film is wound around the shaft. A leader portion of the film is thrust outside of the patrone through a slit in which fiber material, which is called velvet, is arranged.
The patrone in which a 35 mm roll film is accommodated is on the market in Japan, and is made of metal. However, it has the following problems: a problem of manufacturing cost, a problem of film loading into a camera, a problem of making it smaller, a problem of recycling, and the like. Therefore, various kinds of plastic patrones or cartridges, which are standardized as a cartridge in this specification, have been proposed in, for example, Japanese Patent Publication Open to Public Inspection No. 214,153/1991, and U.S. Pat. No. 5,031,852.
The cartridge disclosed in those publications is identical to that shown in FIG. 6, and the following points are greatly different from the cartridge for a 35 mm photographic roll film which is currently used. Firstly, the cartridge is not made of a metal, but made of synthetic resin; the leading edge of the film is pulled into the casing, and a leader portion is not exposed outside the casing, or a small portion of the leading edge portion of the film is exposed; and an accommodated film can be easily pulled into the casing or pulled out of the casing when a spool shaft of the cartridge is rotated. That is, the film cartridge is a so-called "non-leader portion type", and a new technology corresponding to various technical problems, which is not provided in the conventional metallic cartridge, is adopted in the film cartridge as follows: the leading edge of a film 53 is wound inside a cartridge main body 50, or fed outside the cartridge main body 50.
It is performed by the same mechanism as that of a conventional metallic patrone in that the film 53 is wound into the cartridge main body 50, because the base end of the film 53 is fixed to the spool shaft 54 (see FIG. 7) and the spool shaft 54 can only be rotated in the direction in which the film is wound into the cartridge main body. However, when the leading edge of the film 53 is wound into the cartridge main body 50, the structure, in which the film 53 is again fed out of the cartridge main body 50, should be considered, and the following special structure is adopted into the cartridge main body.
That is, as shown in the prior art of FIG. 7, flexible flanges 60 made of synthetic resin are prepared on both end portions of the spool shaft 54 in the manner that the flanges are sandwiched in between hubs 55 and 56. Both end portions of the film 53 wound around the spool shaft 54 are pressed by rising portions 61 of the flanges 60 in order to prevent the film 53 from loosening and spreading like a spring. When the film 53 is not loosened as described above, the leading edge of the film 53 can be thrust out of the cartridge main body 50 according to the rotation of the spool shaft 54 by operating hubs 55 and 56.
A vacuum forming manufacturing method of the flange is disclosed in Japanese Patent Publication Open to Public Inspection No. 251,841/1992.
As a synthetic resin forming method, the following methods are enumerated: vacuum forming and thermal press-forming in which a resin sheet is used as material; injection molding in which resin pellets are used as material. It is widely known that these methods can be equally and effectively used in industry.
However, as a result of investigations by the inventors, the following disadvantages could be found in the flanges manufactured by the method disclosed in Japanese Patent Publication Open to Public Inspection No. 251841/1992: torque values when the film is pulled out of or wound into the cartridges fluctuated widely; and the photographic performance of the unexposed film was severely influenced by undetermined causes. Further, when a film in which a magnetic recording layer was provided as disclosed in U.S. Pat. No. 4,864,332 and U.S. Pat. No. 4,965,627 was used for a cartridge with flanges manufactured by the foregoing Japanese Patent Publication Open to Public Inspection No. 251841/1992, defects caused by unknown causes were found.
In view of the foregoing, the object of the present invention is to provide a manufacturing method for flanges in which: the quality is uniform; the performance of a film accommodated in the cartridge is not deteriorated; the productivity of cartridges is excellent; and the manufacturing cost is low.